این مطالعه کلیفاژهای مختلف را از فاضلاب شهری تصفیه شده جدا کرد. کولیفاژها ویروس هایی هستند که باکتری E.coli را آلوده می کنند و می توانند به عنوان مدلی برای ویروس های روده انسان در مطالعات ضد عفونی استفاده شوند. تقریباً نیمی از کلیفاژهای جدا شده در برابر کلر یا اشعه ماوراء بنفش بسیار مقاوم بودند و به همین دلیل است که نه کلر و نه اشعه ماوراء بنفش به تنهایی در برابر همه کلیفاژها مؤثر نبودند.
"This highlights the importance of a combined treatment," says Doctoral Student Alyaa Zyara, MSc, from the University of Eastern Finland, who presented the results in her doctoral dissertation.
هنگامی که کلیفاژها برای اولین بار در معرض غلظت کم کلر ({0}}.1 یا 0.5 میلی گرم کلر در لیتر) به مدت 10 دقیقه و به دنبال آن اشعه ماوراء بنفش کم (فقط 22 mWs/cm2) قرار گرفتند، بیش از 99.9 درصد تمام کلیفاژهای مورد مطالعه غیرفعال شدند. با این حال، هنگامی که ترتیب درمان معکوس شد (اول UV، دوم کلر)، ضد عفونی بسیار کمتر موثر بود.
"It is more effective to first use a low dosage of chlorine followed by a low dosage of UV radiation than to use high chlorine or UV dosages alone. The order of treatment is also important: using UV radiation first and chlorine second was less effective. In other words, the combination treatment using chlorine first and UV second can be recommended as a disinfection method for viruses."
The study also tested novel UV-LED technology, as UV-LEDs are a new method for disinfecting drinking water. The study used UV-LEDs operating at a wavelength of 270 nm and with a 120 mW irradiation capacity, which haven't been used in disinfection studies before. As little as 2 minutes of this UV-LED treatment was enough to cause a 90-99.9 percent reduction in the coliphages tested in a 5.2-litre reactor. Irradiation time of 10 minutes in the same reactor increased the reductions to 99.99 -- 99.999 percent . A traditional mercury UV lamp at a 254 nm wavelength caused similar or slightly higher reductions in 2 or 10 minutes, but the water volume was only 10 millilitres.
"UV-LEDs are a promising method for disinfecting water, since they consume less energy than traditional mercury UV lamps. Furthermore, as UV-LEDs do not contain any mercury, they are safer for the environment."
The findings were originally reported in Journal of Water and Health, and Water.
